Brief introduction to Active filter circuits.
Active filters using opamps have some advantages over passive
filters particularly at low frequencies.
Active filters can be constructed without large inductors using only opamps, resistors and capacitors.
They can be designed with gain.
For higher order filters the transfer function can be factorized
into quadratics and cubics and each factor can be implemented
independently. These filters can then be realized by
connecting first, second and third order sections in series.
Several circuit configurations are possible using general purpose
opamps. Here only a few classic circuits and their
application to basic filter transfer functions will be considered.
Some manufacturers produce special opamps designed to simplify
filter circuits. These manufacturers provide data sheets on the
use of their devices and they will not be considered here.
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COPYRIGHT © 2010 Cuthbert Nyack.